NON-LINEAR VIBRATION ANALYSIS OF A ROBOT ARM

摘要

The possibility of fault detection in structures from changes in their non-linear parameters is one of the actual question of dynamic system monitoring. This study concentrates on signal processing techniques for non-linear system investigation, based on Hilbert transform and envelope and instantaneous frequency, which enables us to estimate system instantaneous dynamic parameters (natural frequencies, damping characteristics and their dependencies on a vibration amplitude and frequency) during free vibration analysis and different kinds of excitation of the system. The direct time domain techniques allow a direct extraction of the linear and non-linear systems parameters from the measured time signal of input and output. Experimental results of two robot arms testing according to the vibration signal analysis technique have been outlined in this paper. Using an impulse and also a sweep harmonic excitation from the motor (below-after each resonance) we get an input torque signal which together with output vibration signal was used for the modal system analysis. The obtained natural frequency and logarithmic decrement are dependent on the input torque level, so the robot system includes non-linearity both in the spring and damping.